Oral care compositions such as mouthwashes, dentifrices and the like often contain active agents for use, for example, in protecting against cavities, plaque, gum problems, tartar build-up and malodour. Measures for enhancing the delivery of such actives, with a view to improving their effectiveness, have been proposed in the art.
For example, GB 1 290 627 (Unilever Ltd) describes the use of sparingly soluble salts of zinc as a means of delivering zinc ions to the oral cavity for use against calculus and plaque on a tooth surface. According to GB 1 290 627 the sparingly soluble zinc salts have another important attribute: they can provide a “reservoir” effect in the mouth. Since the compounds are only slowly dissolved in saliva, they can become lodged in cracks, crevices and interstices between the teeth as well as in dental plaque and other deposits. The zinc ions are released gradually over a period of time, promoting longevity of action against plaque and calculus.
EP 0 434 284 B1 (Johnson & Johnson Consumer Products Inc.) also seeks to provide a source of (bioavailable) zinc ions for use in oral care. According to EP 0 434 281, this is achieved by the use of an aqueous liquid mouthwash composition of a zinc salt including a pharmaceutically acceptable zinc salt codissolved with a complexing agent selected from the group consisting of sodium gluconate, maleic acid, aspartic acid, gluconic acid, succinic acid, glucuronic acid, sodium glutamate and fumaric acid, in a naturally derived anionic polymer of sodium carboxymethylcellulose or sodium alginate, the composition having a pH of from 5.7 to 6.5.
EP 0 558 586 B1 (Pharmacia AB) discloses that certain water-soluble non-ionic cellulose ethers in combination with a charged surfactant in water have the property of being liquid at room temperature and forming a gel when warmed to body temperature. Such properties can be used for specialized drug delivery. EP 0 558 586 B1 discloses that when a mouth rinse solution, according to the invention therein, contains a suitable anionic surfactant it is possible to incorporate fluoride ions for anti-caries treatment. After being warmed up in the mouth the solution is transformed to a gel which sticks to the mucous membrane in a thin layer. The gel then provides a source of fluoride ions which are slowly released to the saliva.
GB 2 235 133A (Colgate-Palmolive Company) discloses that the anti-plaque effectiveness of an antibacterial agent such as 2,4,4′-trichloro-2′-hydroxyldiphenyl ether (triclosan) is enhanced by the use of an antibacterial-enhancing agent (AEA). Suitable AEAs are disclosed as including anionic polymers such as maleic acid-methyl vinyl ether copolymer or a polymer containing phosphonic groups. According to GB 2 235 133A the AEA contains at least one delivery enhancing group and at least one organic retention-enhancing group or preferably a plurality of both groups.
U.S. Pat. No. 5,496,541 (Pilot Research & Development Co) relates to dental products containing a ternary surfactant system. According to U.S. Pat. No. 5,496,541 excellent adhesion to tooth surfaces and oral mucosa is achieved by the use of a poloxamer-anionic polysaccharide-nonionic cellulose ether surfactant system, which enhances the beneficial effects of the surfactant system and of the other active ingredients in the formulation.
According to EP 0 864 315B1 (Sunstar Inc.), measures for enhancing the adhesive properties of preparations containing a drug (a cationic bactericide) have been proposed in the art for improving the effectiveness of the bactericide. A generally employed technique for improving the adhesion of a preparation to wet surfaces e.g. the mucous membrane in the oral cavity, is described as incorporating in the preparation a carboxyvinyl polymer, polyacrylic acid, or an analogue thereof, which each show excellent adhesion to the mucous membrane in the oral cavity. Examples of such preparations include solid preparations for oral use such as the high-viscosity gel containing a carboxyvinyl polymer and a hydroxypropylmethyl cellulose (HPMC) in combination described in JP-A-7 267839. However according to the inventors therein, such conventional preparations still have the problem that the cationic bactericide loses bactericidal activity when used in combination with an anionic ingredient e.g. a carboxyvinyl polymer. According to EP 0 864 315B1, this problem is solved by using a specific hydroxypropyl methyl cellulose which is incorporated as a thickener into the liquid oral preparation. Apparently such a preparation adheres well to oral tissues, especially to the surfaces of teeth. The Examples in EP 0 864 315B1 include comparative examples of formulations that comprise alternative cellulose ether thickeners to HPMC. The alternative cellulose thickeners investigated alongside the cationic bactericide, cetyl pyridinium chloride, include hydroxethyl cellulose, hydroxypropyl cellulose and methyl cellulose.
US2004/0062724 (Daniel G. Moro et al) discloses a further alternative means of delivering an active compound to teeth surfaces. US2004/0062724 discloses an erodible multilayered strip comprising at least two layers, a first layer comprising a water-soluble polymer or a combination of polymers that adheres to moist enamel surfaces and a second non-adhesive backing layer that is water-erodible and controls the residence time of the strip. The adhesive polymers are disclosed as being any water-soluble FDA approved polymers for oral applications that stick to an enamel surface when in contact with a moist tooth surface. The adhesive polymers may comprise hydroxyethyl cellulose, hydroxypropyl cellulose, hydroxypropylmethyl cellulose, hydroxymethyl cellulose, sodium carboxymethyl cellulose, polyvinyl pyrrolidone, polyvinyl alcohol, polyethylene glycol, polyacrylic acid, polyethylene oxide alone or in combination thereof. The preferred adhesive polymers are hydroxyethyl cellulose and polyvinyl pyrrolidone.
According to the present invention there is provided an oral care composition comprising hydroxypropyl cellulose, which serves to increase delivery of an active agent to soft tissues and related surfaces in the oral cavity.